Adenylate cyclase and cyclic AMP in the ciliate Euplotes crassus: Involvement in both cell cycle and sexual reproduction

Abstract

AbstractIn this paper the presence and the possible activity of adenylate cyclase‐cyclic AMP (AC‐cAMP) system has been investigated through cell cycle and sexual reproduction of the ciliate Euplotes crassus. For this purpose cytochemical studies for AC demonstration at the ultrastructural level were carried on. Moreover, “in‐vivo” experiments were performed by adding different substances to the cell cultures: alloxan (inhibitor of AC), theophylline (inhibitor of phosphodiesterase), exogenous cAMP, and cholera toxin (which maintains AC in an active state). The results obtained are indicative that cAMP is a “regulatory factor” acting during cell cycle as E. crassus cells are not able to undergo macronuclear DNA synthesis in the presence of theophylline. As concerns sexual reproduction both cytochemical observation and “in‐vivo” experiments are suggestive of a rapid activation of AC upon mixing strains of different mating types. This activation, which lasts only for the initial part of the waiting period, appears to be necessary for pair formation.